Struts2源码分析-请求处理（转载）

Struts2源码分析--请求处理（转载）

Struts2架构图


??????? 请求首先通过Filter chain，Filter主要包括ActionContextCleanUp，它主要清理当前线程的ActionContext和Dispatcher；FilterDispatcher主要通过AcionMapper来决定需要调用哪个Action。
??????? ActionMapper取得了ActionMapping后，在Dispatcher的serviceAction方法里创建ActionProxy，ActionProxy创建ActionInvocation，然后ActionInvocation调用Interceptors，执行Action本身，创建Result并返回，当然，如果要在返回之前做些什么，可以实现PreResultListener。

Struts2部分类介绍
这部分从Struts2参考文档中翻译就可以了。
ActionMapper
??????? ActionMapper其实是HttpServletRequest和Action调用请求的一个映射，它屏蔽了Action对于Request等java Servlet类的依赖。Struts2中它的默认实现类是DefaultActionMapper，ActionMapper很大的用处可以根据自己的需要来设计url格式，它自己也有Restful的实现，具体可以参考文档的docs\actionmapper.html。
ActionProxy&ActionInvocation
??????? Action的一个代理，由ActionProxyFactory创建，它本身不包括Action实例，默认实现DefaultActionProxy是由ActionInvocation持有Action实例。ActionProxy作用是如何取得Action，无论是本地还是远程。而ActionInvocation的作用是如何执行Action，拦截器的功能就是在ActionInvocation中实现的。
ConfigurationProvider&Configuration
??????? ConfigurationProvider就是Struts2中配置文件的解析器，Struts2中的配置文件主要是尤其实现类XmlConfigurationProvider及其子类StrutsXmlConfigurationProvider来解析，

Struts2请求流程
1、客户端发送请求
2、请求先通过ActionContextCleanUp-->FilterDispatcher
3、FilterDispatcher通过ActionMapper来决定这个Request需要调用哪个Action
4、如果ActionMapper决定调用某个Action，FilterDispatcher把请求的处理交给ActionProxy，这儿已经转到它的Delegate--Dispatcher来执行
5、ActionProxy根据ActionMapping和ConfigurationManager找到需要调用的Action类
6、ActionProxy创建一个ActionInvocation的实例
7、ActionInvocation调用真正的Action，当然这涉及到相关拦截器的调用
8、Action执行完毕，ActionInvocation创建Result并返回，当然，如果要在返回之前做些什么，可以实现PreResultListener。添加PreResultListener可以在Interceptor中实现，不知道其它还有什么方式？

Struts2(2.1.2)部分源码阅读
??? 从org.apache.struts2.dispatcher.FilterDispatcher开始
??? //创建Dispatcher，此类是一个Delegate，它是真正完成根据url解析，读取对应Action的地方
??? public void init(FilterConfig filterConfig) throws ServletException {
??????? try {
??????????? this.filterConfig = filterConfig;

??????????? initLogging();

??????????? dispatcher = createDispatcher(filterConfig);
??????????? dispatcher.init();
??????????? dispatcher.getContainer().inject(this);
??????????? //读取初始参数pakages，调用parse()，解析成类似/org/apache/struts2/static,/template的数组
??????????? String param = filterConfig.getInitParameter("packages");
??????????? String packages = "org.apache.struts2.static template org.apache.struts2.interceptor.debugging";
??????????? if (param != null) {
??????????????? packages = param + " " + packages;
??????????? }
??????????? this.pathPrefixes = parse(packages);
??????? } finally {
??????????? ActionContext.setContext(null);
??????? }
??? }
???? 顺着流程我们看Disptcher的init方法。init方法里就是初始读取一些配置文件等，先看init_DefaultProperties，主要是读取properties配置文件。
??? private void init_DefaultProperties() {
??????? configurationManager.addConfigurationProvider(new DefaultPropertiesProvider());
??? }
??? 打开DefaultPropertiesProvider
??? public void register(ContainerBuilder builder, LocatableProperties props)
??????????? throws ConfigurationException {
???????
??????? Settings defaultSettings = null;
??????? try {
??????????? defaultSettings = new PropertiesSettings("org/apache/struts2/default");
??????? } catch (Exception e) {
??????????? throw new ConfigurationException("Could not find or error in org/apache/struts2/default.properties", e);
??????? }
???????
??????? loadSettings(props, defaultSettings);
??? }

??? //PropertiesSettings
??? //读取org/apache/struts2/default.properties的配置信息，如果项目中需要覆盖，可以在classpath里的struts.properties里覆写
??? public PropertiesSettings(String name) {
???????
??????? URL settingsUrl = ClassLoaderUtils.getResource(name + ".properties", getClass());
???????
??????? if (settingsUrl == null) {
??????????? LOG.debug(name + ".properties missing");
??????????? settings = new LocatableProperties();
??????????? return;
??????? }
???????
??????? settings = new LocatableProperties(new LocationImpl(null, settingsUrl.toString()));

??????? // Load settings
??????? InputStream in = null;
??????? try {
??????????? in = settingsUrl.openStream();
??????????? settings.load(in);
??????? } catch (IOException e) {
??????????? throw new StrutsException("Could not load " + name + ".properties:" + e, e);
??????? } finally {
??????????? if(in != null) {
??????????????? try {
??????????????????? in.close();
??????????????? } catch(IOException io) {
??????????????????? LOG.warn("Unable to close input stream", io);
??????????????? }
??????????? }
??????? }
??? }
??? 再来看init_TraditionalXmlConfigurations方法，这个是读取struts-default.xml和Struts.xml的方法。
??? private void init_TraditionalXmlConfigurations() {
??????? //首先读取web.xml中的config初始参数值
??????? //如果没有配置就使用默认的"struts-default.xml,struts-plugin.xml,struts.xml"，
??????? //这儿就可以看出为什么默认的配置文件必须取名为这三个名称了
??????? //如果不想使用默认的名称，直接在web.xml中配置config初始参数即可
??????? String configPaths = initParams.get("config");
??????? if (configPaths == null) {
??????????? configPaths = DEFAULT_CONFIGURATION_PATHS;
??????? }
??????? String[] files = configPaths.split("\\s*[,]\\s*");
??????? //依次解析配置文件，xwork.xml单独解析
??????? for (String file : files) {
??????????? if (file.endsWith(".xml")) {
??????????????? if ("xwork.xml".equals(file)) {
??????????????????? configurationManager.addConfigurationProvider(new XmlConfigurationProvider(file, false));
??????????????? } else {
??????????????????? configurationManager.addConfigurationProvider(new StrutsXmlConfigurationProvider(file, false, servletContext));
??????????????? }
??????????? } else {
??????????????? throw new IllegalArgumentException("Invalid configuration file name");
??????????? }
??????? }
??? }
??? 对于其它配置文件只用StrutsXmlConfigurationProvider，此类继承XmlConfigurationProvider，而XmlConfigurationProvider又实现ConfigurationProvider接口。类XmlConfigurationProvider负责配置文件的读取和解析，addAction()方法负责读取<action>标签，并将数据保存在ActionConfig中；addResultTypes()方法负责将<result-type>标签转化为ResultTypeConfig对象；loadInterceptors()方法负责将<interceptor>标签转化为InterceptorConfi对象；loadInterceptorStack()方法负责将<interceptor-ref>标签转化为InterceptorStackConfig对象；loadInterceptorStacks()方法负责将<interceptor-stack>标签转化成InterceptorStackConfig对象。而上面的方法最终会被addPackage()方法调用，将所读取到的数据汇集到PackageConfig对象中。来看XmlConfigurationProvider的源代码，详细的我自己也就大体浏览了一下，各位可以自己研读。
??? protected PackageConfig addPackage(Element packageElement) throws ConfigurationException {
??????? PackageConfig.Builder newPackage = buildPackageContext(packageElement);

??????? if (newPackage.isNeedsRefresh()) {
??????????? return newPackage.build();
??????? }
??????? .

??????? addResultTypes(newPackage, packageElement);
??????? loadInterceptors(newPackage, packageElement);
??????? loadDefaultInterceptorRef(newPackage, packageElement);
??????? loadDefaultClassRef(newPackage, packageElement);
??????? loadGlobalResults(newPackage, packageElement);
??????? loadGobalExceptionMappings(newPackage, packageElement);
??????? NodeList actionList = packageElement.getElementsByTagName("action");

??????? for (int i = 0; i < actionList.getLength(); i++) {
??????????? Element actionElement = (Element) actionList.item(i);
??????????? addAction(actionElement, newPackage);
??????? }
??????? loadDefaultActionRef(newPackage, packageElement);
??????? PackageConfig cfg = newPackage.build();
??????? configuration.addPackageConfig(cfg.getName(), cfg);
??????? return cfg;
??? }
??? 这儿发现一个配置上的小技巧，我的xwork2.0.*是没有的，但是看源码是看到xwork2.1.*是可以的。继续看XmlConfigurationProvider的源代码：
??? private List loadConfigurationFiles(String fileName, Element includeElement) {
??????? List<Document> docs = new ArrayList<Document>();
??????? if (!includedFileNames.contains(fileName)) {
???????????????
??????????????? Element rootElement = doc.getDocumentElement();
??????????????? NodeList children = rootElement.getChildNodes();
??????????????? int childSize = children.getLength();

??????????????? for (int i = 0; i < childSize; i++) {
??????????????????? Node childNode = children.item(i);

??????????????????? if (childNode instanceof Element) {
??????????????????????? Element child = (Element) childNode;

??????????????????????? final String nodeName = child.getNodeName();
??????????????????????? //解析每个action配置是，对于include文件可以使用通配符*来进行配置
??????????????????????? //如Struts.xml中可配置成<include file="actions_*.xml"/>
??????????????????????? if (nodeName.equals("include")) {
??????????????????????????? String includeFileName = child.getAttribute("file");
??????????????????????????? if(includeFileName.indexOf('*') != -1 ) {
??????????????????????????????? ClassPathFinder wildcardFinder = new ClassPathFinder();
??????????????????????????????? wildcardFinder.setPattern(includeFileName);
??????????????????????????????? Vector<String> wildcardMatches = wildcardFinder.findMatches();
??????????????????????????????? for (String match : wildcardMatches) {
??????????????????????????????????? docs.addAll(loadConfigurationFiles(match, child));
??????????????????????????????? }
??????????????????????????? }
??????????????????????????? else {
???????????????????????????????
??????????????????????????????? docs.addAll(loadConfigurationFiles(includeFileName, child));???
??????????????????????????? }???
??????????????????? }
??????????????? }
??????????????? }
??????????????? docs.add(doc);
??????????????? loadedFileUrls.add(url.toString());
??????????? }
??????? }
??????? return docs;
??? }
??? init_CustomConfigurationProviders方式初始自定义的Provider，配置类全名和实现ConfigurationProvider接口，用逗号隔开即可。
??? private void init_CustomConfigurationProviders() {
??????? String configProvs = initParams.get("configProviders");
??????? if (configProvs != null) {
??????????? String[] classes = configProvs.split("\\s*[,]\\s*");
??????????? for (String cname : classes) {
??????????????? try {
??????????????????? Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
??????????????????? ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
??????????????????? configurationManager.addConfigurationProvider(prov);
??????????????? }
???????????????
??????????? }
??????? }
??? }
??? 好了，现在再回到FilterDispatcher，每次发送一个Request，FilterDispatcher都会调用doFilter方法。
??? public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

??????? HttpServletRequest request = (HttpServletRequest) req;
??????? HttpServletResponse response = (HttpServletResponse) res;
??????? ServletContext servletContext = getServletContext();

??????? String timerKey = "FilterDispatcher_doFilter: ";
??????? try {
??????????? ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
??????????? ActionContext ctx = new ActionContext(stack.getContext());
??????????? ActionContext.setContext(ctx);
???????????
??????????? UtilTimerStack.push(timerKey);
??????????? //根据content type来使用不同的Request封装，可以参见Dispatcher的wrapRequest
??????????? request = prepareDispatcherAndWrapRequest(request, response);
??????????? ActionMapping mapping;
??????????? try {
??????????????? //根据url取得对应的Action的配置信息--ActionMapping，actionMapper是通过Container的inject注入的
??????????????? mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
??????????? } catch (Exception ex) {
??????????????? log.error("error getting ActionMapping", ex);
??????????????? dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
??????????????? return;
??????????? }
??????????? //如果找不到对应的action配置，则直接返回。比如你输入***.jsp等等
??????????? //这儿有个例外，就是如果path是以“/struts”开头，则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中，当然.class文件除外。如果再没有则跳转到404
??????????? if (mapping == null) {
??????????????? // there is no action in this request, should we look for a static resource?
??????????????? String resourcePath = RequestUtils.getServletPath(request);

??????????????? if ("".equals(resourcePath) && null != request.getPathInfo()) {
??????????????????? resourcePath = request.getPathInfo();
??????????????? }

??????????????? if (serveStatic && resourcePath.startsWith("/struts")) {
??????????????????? String name = resourcePath.substring("/struts".length());
??????????????????? findStaticResource(name, request, response);
??????????????? } else {
??????????????????? chain.doFilter(request, response);
??????????????? }
??????????????? return;
??????????? }
??????????? //正式开始Action的方法了
??????????? dispatcher.serviceAction(request, response, servletContext, mapping);

??????? } finally {
??????????? try {
??????????????? ActionContextCleanUp.cleanUp(req);
??????????? } finally {
??????????????? UtilTimerStack.pop(timerKey);
??????????? }
??????? }
??? }
??? Dispatcher类的serviceAction方法：
??? public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping) throws ServletException {

??????? Map<String, Object> extraContext = createContextMap(request, response, mapping, context);

??????? // If there was a previous value stack, then create a new copy and pass it in to be used by the new Action
??????? ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);
??????? if (stack != null) {
??????????? extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));
??????? }

??????? String timerKey = "Handling request from Dispatcher";
??????? try {
??????????? UtilTimerStack.push(timerKey);
??????????? String namespace = mapping.getNamespace();
??????????? String name = mapping.getName();
??????????? String method = mapping.getMethod();

??????????? Configuration config = configurationManager.getConfiguration();
??????????? ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
??????????????????? namespace, name, method, extraContext, true, false);

??????????? request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());

??????????? // if the ActionMapping says to go straight to a result, do it!
??????????? if (mapping.getResult() != null) {
??????????????? Result result = mapping.getResult();
??????????????? result.execute(proxy.getInvocation());
??????????? } else {
??????????????? proxy.execute();
??????????? }

??????????? // If there was a previous value stack then set it back onto the request
??????????? if (stack != null) {
??????????????? request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
??????????? }
??????? } catch (ConfigurationException e) {
??????????? LOG.error("Could not find action or result", e);
??????????? sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
??????? } catch (Exception e) {
??????????? sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
??????? } finally {
??????????? UtilTimerStack.pop(timerKey);
??????? }
??? }
??? 第一句createContextMap()方法，该方法主要把Application、Session、Request的key value值拷贝到Map中，并放在HashMap<String,Object>中，可以参见createContextMap方法：
??? public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
??????????? ActionMapping mapping, ServletContext context) {

??????? // request map wrapping the http request objects
??????? Map requestMap = new RequestMap(request);
??????? // parameters map wrapping the http parameters.? ActionMapping parameters are now handled and applied separately
??????? Map params = new HashMap(request.getParameterMap());
??????? // session map wrapping the http session
??????? Map session = new SessionMap(request);
??????? // application map wrapping the ServletContext
??????? Map application = new ApplicationMap(context);
??????? Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
??????? extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
??????? return extraContext;
??? }
??? 后面才是最主要的--ActionProxy，ActionInvocation。ActionProxy是Action的一个代理类，也就是说Action的调用是通过ActionProxy实现的，其实就是调用了ActionProxy.execute()方法，而该方法又调用了ActionInvocation.invoke()方法。归根到底，最后调用的是DefaultActionInvocation.invokeAction()方法。先看DefaultActionInvocation的init方法。
??? public void init(ActionProxy proxy) {
??????? this.proxy = proxy;
??????? Map contextMap = createContextMap();

??????? // Setting this so that other classes, like object factories, can use the ActionProxy and other
??????? // contextual information to operate
??????? ActionContext actionContext = ActionContext.getContext();

??????? if(actionContext != null) {
??????????? actionContext.setActionInvocation(this);
??????? }
??????? //创建Action，可Struts2里是每次请求都新建一个Action
??????? createAction(contextMap);

??????? if (pushAction) {
??????????? stack.push(action);
??????????? contextMap.put("action", action);
??????? }

??????? invocationContext = new ActionContext(contextMap);
??????? invocationContext.setName(proxy.getActionName());

??????? // get a new List so we don't get problems with the iterator if someone changes the list
??????? List interceptorList = new ArrayList(proxy.getConfig().getInterceptors());
??????? interceptors = interceptorList.iterator();
??? }

??? protected void createAction(Map contextMap) {
??????? // load action
??????? String timerKey = "actionCreate: "+proxy.getActionName();
??????? try {
??????????? UtilTimerStack.push(timerKey);
??????????? //这儿默认建立Action是StrutsObjectFactory，实际中我使用的时候都是使用Spring创建的Action，这个时候使用的是SpringObjectFactory
??????????? action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
??????? }
??????? ..
??????? } finally {
??????????? UtilTimerStack.pop(timerKey);
??????? }

??????? if (actionEventListener != null) {
??????????? action = actionEventListener.prepare(action, stack);
??????? }
??? }
??? 接下来看看DefaultActionInvocation 的invoke方法。
?? public String invoke() throws Exception {
??????? String profileKey = "invoke: ";
??????? try {
??????????? UtilTimerStack.push(profileKey);
???????????
??????????? if (executed) {
??????????????? throw new IllegalStateException("Action has already executed");
??????????? }
??????????????? //先执行interceptors
??????????? if (interceptors.hasNext()) {
??????????????? final InterceptorMapping interceptor = (InterceptorMapping) interceptors.next();
??????????????? UtilTimerStack.profile("interceptor: "+interceptor.getName(),
??????????????????????? new UtilTimerStack.ProfilingBlock<String>() {
??????????????????????????? public String doProfiling() throws Exception {
??????????????????????????????? resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
??????????????????????????????? return null;
??????????????????????????? }
??????????????? });
??????????? } else {
??????????????????????? //interceptor执行完了之后执行action
??????????????? resultCode = invokeActionOnly();
??????????? }

??????????? // this is needed because the result will be executed, then control will return to the Interceptor, which will
??????????? // return above and flow through again
??????????? if (!executed) {
??????????????????????? //在Result返回之前调用preResultListeners
??????????????? if (preResultListeners != null) {
??????????????????? for (Iterator iterator = preResultListeners.iterator();
??????????????????????? iterator.hasNext();) {
??????????????????????? PreResultListener listener = (PreResultListener) iterator.next();
???????????????????????
??????????????????????? String _profileKey="preResultListener: ";
??????????????????????? try {
??????????????????????????? UtilTimerStack.push(_profileKey);
??????????????????????????? listener.beforeResult(this, resultCode);
??????????????????????? }
??????????????????????? finally {
??????????????????????????? UtilTimerStack.pop(_profileKey);
??????????????????????? }
??????????????????? }
??????????????? }

??????????????? // now execute the result, if we're supposed to
??????????????? if (proxy.getExecuteResult()) {
??????????????????? executeResult();
??????????????? }

??????????????? executed = true;
??????????? }

??????????? return resultCode;
??????? }
??????? finally {
??????????? UtilTimerStack.pop(profileKey);
??????? }
??? }
??? 看程序中的if(interceptors.hasNext())语句，当然，interceptors里存储的是interceptorMapping列表（它包括一个Interceptor和一个name），所有的截拦器必须实现Interceptor的intercept方法，而该方法的参数恰恰又是ActionInvocation，在intercept方法中还是调用invocation.invoke()，从而实现了一个Interceptor链的调用。当所有的Interceptor执行完，最后调用invokeActionOnly方法来执行Action相应的方法。
??? protected String invokeAction(Object action, ActionConfig actionConfig) throws Exception {
??????? String methodName = proxy.getMethod();
??????? String timerKey = "invokeAction: "+proxy.getActionName();
??????? try {
??????????? UtilTimerStack.push(timerKey);
???????????
??????????? boolean methodCalled = false;
??????????? Object methodResult = null;
??????????? Method method = null;
??????????? try {
??????????????? //获得需要执行的方法
??????????????? method = getAction().getClass().getMethod(methodName, new Class[0]);
??????????? } catch (NoSuchMethodException e) {
??????????????? //如果没有对应的方法，则使用do+Xxxx来再次获得方法
??????????????? try {
??????????????????? String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1);
??????????????????? method = getAction().getClass().getMethod(altMethodName, new Class[0]);
??????????????? } catch (NoSuchMethodException e1) {
??????????????????? // well, give the unknown handler a shot
??????????????????? if (unknownHandler != null) {
??????????????????????? try {
??????????????????????????? methodResult = unknownHandler.handleUnknownActionMethod(action, methodName);
??????????????????????????? methodCalled = true;
??????????????????????? } catch (NoSuchMethodException e2) {
??????????????????????????? // throw the original one
??????????????????????????? throw e;
??????????????????????? }
??????????????????? } else {
??????????????????????? throw e;
??????????????????? }
??????????????? }
??????????? }
???????????
??????????? if (!methodCalled) {
??????????????? methodResult = method.invoke(action, new Object[0]);
??????????? }
??????????? //根据不同的Result类型返回不同值
??????????? //如输出流Result
??????????? if (methodResult instanceof Result) {
??????????????? this.explicitResult = (Result) methodResult;
??????????????? return null;
??????????? } else {
??????????????? return (String) methodResult;
??????????? }
??????? } catch (NoSuchMethodException e) {
??????????? throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");
??????? } catch (InvocationTargetException e) {
??????????? // We try to return the source exception.
??????????? Throwable t = e.getTargetException();

??????????? if (actionEventListener != null) {
??????????????? String result = actionEventListener.handleException(t, getStack());
??????????????? if (result != null) {
??????????????????? return result;
??????????????? }
??????????? }
??????????? if (t instanceof Exception) {
??????????????? throw(Exception) t;
??????????? } else {
??????????????? throw e;
??????????? }
??????? } finally {
??????????? UtilTimerStack.pop(timerKey);
??????? }
??? }
??? 好了，action执行完了，还要根据ResultConfig返回到view，也就是在invoke方法中调用executeResult方法。
??? private void executeResult() throws Exception {
??????? //根据ResultConfig创建Result
??????? result = createResult();
??????? String timerKey = "executeResult: "+getResultCode();
??????? try {
??????????? UtilTimerStack.push(timerKey);
??????????? if (result != null) {
??????????????? //这儿正式执行:)
??????????????? //可以参考Result的实现，如用了比较多的ServletDispatcherResult,ServletActionRedirectResult,ServletRedirectResult
??????????????? result.execute(this);
??????????? } else if (resultCode != null && !Action.NONE.equals(resultCode)) {
??????????????? throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()
??????????????????????? + " and result " + getResultCode(), proxy.getConfig());
??????????? } else {
??????????????? if (LOG.isDebugEnabled()) {
??????????????????? LOG.debug("No result returned for action "+getAction().getClass().getName()+" at "+proxy.getConfig().getLocation());
??????????????? }
??????????? }
??????? } finally {
??????????? UtilTimerStack.pop(timerKey);
??????? }
??? }
??? public Result createResult() throws Exception {
??????? if (explicitResult != null) {
??????????? Result ret = explicitResult;
??????????? explicitResult = null;;
??????????? return ret;
??????? }
??????? ActionConfig config = proxy.getConfig();
??????? Map results = config.getResults();
??????? ResultConfig resultConfig = null;
??????? synchronized (config) {
??????????? try {
??????????????? //根据result名称获得ResultConfig，resultCode就是result的name
??????????????? resultConfig = (ResultConfig) results.get(resultCode);
??????????? } catch (NullPointerException e) {
??????????? }
??????????? if (resultConfig == null) {
??????????????? //如果找不到对应name的ResultConfig，则使用name为*的Result
??????????????? resultConfig = (ResultConfig) results.get("*");
??????????? }
??????? }
??????? if (resultConfig != null) {
??????????? try {
??????????????? //参照StrutsObjectFactory的代码
??????????????? Result result = objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
??????????????? return result;
??????????? } catch (Exception e) {
??????????????? LOG.error("There was an exception while instantiating the result of type " + resultConfig.getClassName(), e);
??????????????? throw new XWorkException(e, resultConfig);
??????????? }
??????? } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandler != null) {
??????????? return unknownHandler.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
??????? }
??????? return null;
??? }
??? //StrutsObjectFactory
??? public Result buildResult(ResultConfig resultConfig, Map extraContext) throws Exception {
??????? String resultClassName = resultConfig.getClassName();
??????? if (resultClassName == null)
??????????? return null;
??????? //创建Result，因为Result是有状态的，所以每次请求都新建一个
??????? Object result = buildBean(resultClassName, extraContext);
??????? //这句很重要，后面将会谈到，reflectionProvider参见OgnlReflectionProvider；
??????? //resultConfig.getParams()就是result配置文件里所配置的参数<param></param>
??????? //setProperties方法最终调用的是Ognl类的setValue方法
??????? //这句其实就是把param名值设置到根对象result上
??????? reflectionProvider.setProperties(resultConfig.getParams(), result, extraContext);
??????? if (result instanceof Result)
??????????? return (Result) result;
??????? throw new ConfigurationException(result.getClass().getName() + " does not implement Result.");
??? }
??? 最后补充一下，Struts2的查找值和设置值都是使用Ognl来实现的。关于Ognl的介绍可以到其官方网站查看http://www.ognl.org/，我在网上也找到另外一篇http://www.iteye.com/topic/254684和http://www.iteye.com/topic/223612。完了来看下面这段小测试程序（其它的Ognl的测试可以自己添加）。
public class TestOgnl {
???
??? private User user;
??? private Map context;
???
??? @Before
??? public void setUp() throws Exception {
???
??? }

??? @Test
??? public void ognlGetValue() throws Exception {
??? reset();
??? Assert.assertEquals("myyate", Ognl.getValue("name", user));
??? Assert.assertEquals("cares", Ognl.getValue("dept.name", user));
??? Assert.assertEquals("myyate", Ognl.getValue("name", context, user));
??? Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user));
??? Assert.assertEquals("parker", Ognl.getValue("#pen", context, user));
??? }
???
??? @Test
??? public void ognlSetValue() throws Exception {
??? reset();
??? Ognl.setValue("name", user, "myyateC");
??? Assert.assertEquals("myyateC", Ognl.getValue("name", user));
???
??? Ognl.setValue("dept.name", user, "caresC");
??? Assert.assertEquals("caresC", Ognl.getValue("dept.name", user));
???
??? Assert.assertEquals("contextmap", Ognl.getValue("#name", context, user));
??? Ognl.setValue("#name", context, user, "contextmapC");
??? Assert.assertEquals("contextmapC", Ognl.getValue("#name", context, user));
???
??? Assert.assertEquals("parker", Ognl.getValue("#pen", context, user));
??? Ognl.setValue("#name", context, user, "parkerC");
??? Assert.assertEquals("parkerC", Ognl.getValue("#name", context, user));
??? }
???
??? public static void main(String[] args) throws Exception {
??? JUnitCore.runClasses(TestOgnl.class);
??? }
???
??? private void reset() {
??? user = new User("myyate", new Dept("cares"));
??? context = new OgnlContext();
??? context.put("pen", "parker");
??? context.put("name", "contextmap");
??? }
}

class User {
??? public User(String name, Dept dept) {
??? this.name = name;
??? this.dept = dept;
??? }
??? String name;
??? private Dept dept;
??? public Dept getDept() {
??????? return dept;
??? }
??? public String getName() {
??????? return name;
??? }
??? public void setDept(Dept dept) {
??????? this.dept = dept;
??? }
??? public void setName(String name) {
??????? this.name = name;
??? }
}

class Dept {
??? public Dept(String name) {
??? this.name = name;
??? }
??? private String name;
??? public String getName() {
??????? return name;
??? }
??? public void setName(String name) {
??????? this.name = name;
??? }
}
??? 这样，一个Struts2的请求流程基本上就结束了。其实我觉得做项目把Struts2参考文档看两遍就可以了，呵呵！（写博客比看代码还累）

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